Peroxycarboxylic acids are known for use as antimicrobials and bleaching agents. Mixed peroxycarboxylic acid systems are also known for use as antimicrobial and bleaching agents. However, there are disadvantages to use of these antimicrobial and bleaching agents. For example, the most commonly used peroxycarboxylic acid, peroxyacetic acid, is known to have a strong pungent odor. In addition, peracids (e.g. peroxyacids) such as peroxycarboxylic acid have known chemical disadvantages, namely, they are relatively instable in solution and decompose to ordinary oxyacids and oxygen.
Conventional peroxycarboxylic acid compositions are made through an acid catalyzed equilibrium reaction. Most often, the peroxycarboxylic acids are generated in a chemical plant, and then shipped to customers for on-site use. Due to the limited storage stability of peroxycarboxylic acids, the peroxycarboxylic acids must be packed in special containers and shipped under the strict Department of Transportation (DOT) guidelines. Certain improvements to peroxycarboxylic acid stability have proved advantageous for shipping purposes, as described in U.S. patent application Ser. No. 11/847,604, entitled “Shelf Stable, Reduced Corrosion, Ready to Use Peroxycarboxylic Acid Antimicrobial Compositions,” the entire contents of which are hereby expressly incorporated herein by reference. Most commercially available products in an equilibrium mixture contain excess hydrogen peroxide in the presence of stabilizers and acid catalysts, to stabilize and improve the composition's shelf life. Despite stability improvements, excess amounts of reagents (e.g., acids, oxidizing agents, and stabilizers) are present in the compositions to help form the desired amount of peracids and to prevent decomposition during shipping and storage. These and other disadvantages to the use of equilibrium peracid compositions exist.
Bleach activators are organic compounds with at least one reactive acyl group together with a leaving group. When reacted with a perhydroxyl anion, bleach activators yield an organic peracid in situ. Conventionally this means within a washing machine, whether washer-extractor or continuous batch, i.e. tunnel, washer. Bleach activators have been used to activate peroxygen bleaches, such as hydrogen peroxide, to improve stain removal at lower wash temperatures.
Traditional bleach activators suffer from several limitations. Because the reaction between the activator and the perhydroxyl anion takes place in the dilute wash bath, both the rate and extent of reaction are reduced compared to if the washing solution were more concentrated. Furthermore, the bleach activator must balance between a highly alkaline pH that promotes rapid perhydrolysis and a less alkaline pH where the formed peracid is most effective. It is known that peracids give optimal bleaching close to their pKa value (e.g. pKa 8.2 for peroxyacetic acid). However, conventional bleach activators will exhibit very little perhydrolysis at that low pH. To balance those objectives, a pH value of about 10 is conventionally used for bleach activators, though it is not the optimal point for peracid formation nor peracid performance. Given those limitations, there remains a need for bleach activator system which, by increasing both the concentration and pH, can generate peracids more efficiently. One such method is the on-site generation of peracid compositions that can be generated ex situ to a washing application, such as a washing machine or tunnel washer, at both higher concentration and pH, and then transferred to a washing vessel where the peracid can perform at a lower pH and may optionally be combined in situ with detergents and/or surfactants for synergistic efficacy.
Accordingly, it is an objective of the claimed invention to generate peroxycarboxylic acids and mixed percarboxylic acids on site under alkaline pH for textile bleaching and antimicrobial activity.
It is a further objective of the claimed invention to develop methods of rapidly generating peroxycarboxylic acids and mixed percarboxylic acids at alkaline pH for bleaching applications, including for example textile care. A further object of the invention is to develop methods of rapidly generating peroxycarboxylic acids and mixed percarboxylic acids at alkaline pH for antimicrobial applications, including for example health care and other applications.
A further object of the invention is to utilize on-site methods and/or apparatus for generating stable single and/or mixed peracid and/or peroxyacid systems for use with detergents and/or surfactants for synergistic efficacy.